1. Field of the Invention
The present invention relates to a color-display liquid crystal element for use as color televisions and personal computers, etc., a color filter which is a constituent member of the liquid crystal element, a manufacturing method for the color filter, and to a method for forming spacers applied to the manufacturing method.
2. Description of the Related Art
Recently, demands for color liquid crystal displays are increasing along with the growth of personal computers, especially of portable personal computers. However, the cost-cutting is indispensable for the furthermore widespread use.
In a conventional manufacturing method for the liquid crystal element, after providing liquid crystal driving elements such as TFTs (thin film transistors), or coloring optical elements such as color filters, on glass substrates which are a pair of transparent insulating substrates, respective transparent electrodes and orientation films are formed. Then, over the entire surface of one of the glass substrates having the transparent electrodes and the orientation films formed thereon, perfect spherical or cylindrical particles formed of silica, alumina, a synthetic resin, and so forth having a size of between approximate 3 and 10 xcexcm are generally dispersed as spacers. A liquid crystal element is formed by piling up the pair of glass substrates in the state of the respective transparent electrodes opposing each other via the spacers and by filling the clearance therebetween with liquid crystal.
However, since a transmitting/shielding state of light in an effective pixel portion (light-transmissive portion) is changed according to the display state, when the spacers are formed of a colorless transparent material, they are observed as luminous spots during the shielding while when the spacers are colored to be black, they are observed as black spots during the transmission, so that there has been a problem of reduced display quality.
In order to solve the above-mentioned problem, methods are proposed so that after orientation is performed in the orientation film, photosensitive polyimide or a photoresist is coated thereon so as to form spacers made of polyimide or the photoresist in the region except the effective pixel portion by exposing it to light via a mask, as shown in Japanese Patent Laid-Open No. 61-173221 and Japanese Patent Laid-Open No. 2-223922. According to these methods, since the spacers can be formed at any position in arbitrary density, non-uniformity in the liquid crystal cell gap can be reduced when filling the gap with liquid crystal. Japanese Patent Laid-Open No. 3-94230 also discloses a method for affixing bead spacers on a light-shielding layer in the regions except the effective pixel portions.
Other methods are proposed, such as a method to have a black matrix having large thickness as spacers (Japanese Patent Laid-Open No. 63-237032, Japanese Patent Laid-Open No. 3-184022, and Japanese Patent Laid-Open No. 4-122914, etc.), a method to have pilled up colored resists as spacers (Japanese Patent Laid-Open No. 63-82405), and a method for forming a colored pattern on the black matrix as well to have spacers (Japanese Patent Laid-Open No. 63-237032).
Any of the improved methods disclosed in the above-mentioned publications uses photolithography, so that an expensive exposure system is necessary and there has also been a problem of a long production line due to a wet process such as a developer.
Also, in the improved methods, since photosensitive polyimide or the photoresist is coated over the entire surface and unnecessary portions thereof are removed by solvent, etc., after the coating, there has been a problem of contamination of the effective pixel portions. In particular, when the spacers are formed on an orientation film such as a polyimide film oriented by a rubbing method, etc., the orientational structure formed on the orientation film in the spacer forming process may be significantly contaminated and damaged, thereby, it is feared that orientation of the liquid crystal poured into the liquid crystal cell is to be uneven.
It is also preferable that the spacers be securely affixed on the surface of at least one of substrates so as to maintain the distance between the substrates (cell gap) constant.
Accordingly, it is an object of the present invention to provide a method for forming spacers so that spacers having even height can be readily formed at desired positions in the substrate, and to provide a liquid crystal element being excellent in display quality and having spacers, which are excellent in maintaining the cell gap and do not affect display, at a lower cost by using the method.
In accordance with a first aspect of the present invention, there is provided a method for forming spacers, comprising the steps of: supplying adhesive at a position for forming each of the spacers on the substrate by an inkjet system; dispersing beads, each bead having a diameter corresponding to the height of the spacer, so as to adhere the beads to adhesive; and removing the beads that are not adhered to the adhesive from the substrate.
In accordance with a second aspect of the present invention, there is provided a manufacturing method for a color filter having spacers, the method comprising the steps of: forming a color filter by forming on a substrate at least a light-shielding layer having plural apertures and a colored layer having colored portions arranged in each of the apertures of the light-shielding layer; supplying adhesive made of a curable resin composition in regions overlapping the light-shielding layer on the color filter by an inkjet system; dispersing beads on the color filter so as to stick the beads to the adhesive; and removing the beads that are not adhered to the adhesive from the color filter.
In accordance with a third aspect of the present invention, there is provided a liquid crystal element comprising: a pair of substrates; and liquid crystal clamped between the pair of substrates, wherein one of the pair of substrates is a color filter having spacers made by a manufacturing method according to the present invention and the distance between the pair of substrates is maintained by the spacers.
With these features, in the method for forming spacers according to the present invention, since the beads are adhered and affixed to the adhesive, which is supplied in desired positions by an inkjet system, the spacers can be readily formed in desired positions.
With these features, in the color filter having spacers and the manufacturing method thereof according to the present invention applying the method for forming spacers according to the present invention, the spacers are formed by an inkjet system so that they can be selectively formed on the light-shielding layer, only in the regions, which have not an effect on display, while the beads as the spacers are affixed to the color filter, thereby preventing the spacers from separating in the manufacturing process of the liquid crystal element such as the forming step of the orientation film and after the forming of the liquid crystal element.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.